Microblog: Vacuum and non-magnetic environments

Lens coating in optics technologies, the manufacturing of fiber and laser optics, sensitive detectors, scientific MRI-scanning: it all requires vacuum class environments that vary from low to extreme ultrahigh vacuum. High-end technology evolves with the speed of light. This increases the demand for motion and positioning systems that can be applied in either vacuum or cryogenic environments. Looking for such a precision motion control system? Here’s what you need to know.

Determine the vacuum class, decide on your end goal

To achieve a stable motion control system for vacuum classes from 10-3 to 10-10 hPa, you need to consider the end goal. What do you want your system to do and why? A question that can be answered using the engineered systems-method.

Three steps in developing a vacuum-compatible precision motion system

The first thing you need to decide, to specify the required vacuum level, is what kind of material you need. The outgassing rate and partial pressure of specific residual components are important. For instance, using the wrong grease or plastic components can result in the release of hydrocarbons in a vacuum chamber. In the case of optics surfaces, it can even damage and pollute a test sample. What you need are motorized positioners with low outgassing rates and a residual gas that contains little HC’s, or metals with a high vapor pressure.

Careful design is another major step in creating a suitable precision motion solution. Standard materials need to be substituted for vacuum-compatible materials. The surface of a positioner has to be reduced to a minimum, and virtual leaks are to be prevented. Another important step in the development process is the cleaning, assembling, and packing of the vacuum positioner, which is carefully done with the intention to deliver a sterile system. A detailed description of all these steps can be found in this whitepaper.

Solutions for motions in vacuum and non-magnetic environments

Piezo actuators, made from piezo ceramic material, are one of those elements that are manufactured without polymers, and consequently have a very low gas emission. That makes the material perfect for vacuum-compatible precision motion systems. Better yet, certain types even work in temperatures below 271 degrees Celsius.

Piezoelectric actuators are also exceptionally well-suited for applications where magnetic interference is unwanted. Positioning systems in non-magnetic environments are especially found in medical and biotechnology applications. The piezoelectric motors don’t create any electromagnetic interference, nor are they influenced by it. In strong magnetic fields, like MRI equipment, the actuators perform unimpeded, whereas other electronic motors with metal components make it impossible for motorized medical devices to function in aforementioned apparatus.

Piezo elements are a safe choice, but don’t rule out classic motion yet. Just because traditional motion, like the use of DC or stepper motors, can be a challenge in vacuum and non-magnetic environments, doesn’t mean it’s impossible. Almost all stages can be modified for use in different classes of vacuum and can even be made of several axes. It all depends on the material you use.

When made of aluminum alloys, stainless steels, or titanium, special two-phase stepper motors can operate reliably up to 10-9 hPa. However, you do need a special vacuum lubricant to avoid outgassing and particle emission. To dissipate heat in vacuum environments, you can opt for a classic motion solution with a lower velocity. Your motion system can also be complemented with cables made of PTFE, Teflon, Kapton or PEEK.

Infinite possibilities in vacuum-compatible and non-magnetic positioning technology

All in all, there are quite some aspects you need to consider when you opt for a precision motion solution in vacuum or non-magnetic environments. Let us, and our twenty years of extensive experience in this technology, guide you in the infinite possibilities that PI offers, to solve your high-end motion challenge.  Send me a message by mail or via Linkedin.

 

Sander Slagter
Senior Technical Sales, Engineered Systems at PI Benelux B.V.